To make the lemongrass syrup, place the water, palm sugar and lemongrass in a medium saucepan over high heat and bring to the boil. Reduce heat to low and simmer for 15–20 minutes or until syrup has thickened. Remove lemongrass and set aside.Place the rice, water and vanilla in a medium saucepan over high heat and bring to the boil. Reduce heat to low and simmer for 10 minutes or until most of the water is absorbed. Add the coconut milk and sugar and stir to combine. Reduce heat to low, cover with a tight-fitting lid and cook for a further 5–8 minutes or until the rice is cooked. Top pudding with syrup and serve with mango halves. Serves 4.